bkannek: the stone reefs of brazil. 273 



exposed portions of the reef seems to be solid MilJepore rock, which is 

 certainly being constantly added to by the rapid growth of this species at 

 the present time. This Millepore rock is the most dense and durable of 

 all, though it is extremely brittle, and, because of its mode of growth, is 

 more easily broken than that of either Pontes verriUi or Orhicella axierta. 



Millepm-a hraziliensis grows all over the reef, but in small, isolated 

 heads that add but little to the reef structure. 



Orhicella aperta grows in regular heads that are sometimes two feet 

 or more in diameter, and with an even greater depth of clean, unbroken 

 rock, which is very tough and tenacious. This species would be a 

 very important structural coral if it were more abundant, but it grows 

 only in isolated masses which add comparatively little to the reef. It is 

 found in the more sheltered places of the outer edge of the reef, and 

 forms beautiful, conspicuous heads, because of the large cells and promi- 

 nence of the polyps that look very much like small, encrusting anem- 

 ones. The rock is porous but remarkably tough and durable. 



Mussa harttii is the most striking coral of the Maceio reef. It com- 

 pletely lines the borders of the sheltered lagoons that are constantly 

 filled with the fresh water of the outside. It is a densely branching 

 species forming huge clumps of nearly a solid mass of short thick stems. 

 These clumps rise to a height of ten or fifteen feet in the sheltered coves, 

 but are usually only a foot or so high and as broad along the outer edge 

 of the reef. These smaller clusters grow in the greatest profusion wher- 

 ever the water is clear and the force of the waves is not too great. The 

 thick stems are white surmounted by polyps of a brilliant lavender hue, 

 that are extremely showy because of their large size and bright colors. 

 The stems are very fragile, however, and this species adds to the reef by 

 the accumulation of its broken fragments. After a time the clusters 

 become too heavy for the weak stems, and the waves play havoc with 

 the whole mass, scattering the branches all over the reef. Some of the 

 best collecting of the whole reef is to be had in these Mussa heads, which 

 harbor an immense variety of crustaceans, echinoderms, worms, etc. 



Sympthyllia harttii grows in the same locations as its near relative 

 Musm harttii, and resembles it very strikingly in appearance. The color 

 and size of the polyps are about the same as those of Mus^a, but Sym- 

 phyllia grows in low solid heads, while Miism forms branching clusters. 

 Symphyllia is also very much less abundant than Mussa> 



^ Dr. T. W. Vaughan, to wliom I am indebted for corrections in the nomencla- 

 ture, tells me that Symphi/Uia harttii is, as Verrill at first suspected, only a growth 

 form of Musm harttii. J. C. B. 



VOL. XLIV. 18 



